Assistance needed processing comet C/2022 E3 (ZTF)

[Moonstruck]

HI all,
I need some assistance processing this comet. I took 83 60-sec light frames (with an Esprit 100 refractor, EQ6-R mount and asi 294 camera, using Sharpcap), and stacked them in dss using the comet stacking option (dss comet stacking option 3). This resulted in the below autosave file. When I tried processing it in startools, I got a really poor result- the core of the comet was way too bright and there was a lot of noise surrounding the comet. No comet detail was possible- it is just a glaring bright blob with a barely visible tail. There was also a lot of green blotching in the background which I was not able to get rid of. No matter what I did I could not get it to come out good. It is supposed to have an ion and dust tail, and a green head, and mine came nowhere close to looking as good as other photos I have seen.

If you have time can you take a shot at processing it using the autosave file below? If you are successful please let me know the steps you followed. Not sure where the problems lie with this one! Thanks in advance. John

https://drive.google.com/file/d/15hWBW- ... sp=sharing

[Mike in Rancho]

Hi John,

Well...yikes. I am at a loss.

DSS seems to have done it's job - you have stars and comet. Though how that would compare to running separate stacks and layering them (maybe with a healthy dose of clone stamp or other manipulations if necessary) I don't know. ASTAP also has several comet stacking options.

Granted, a good bit needs to be cropped, but the FOV here is pretty tight. Also, did you use calibration frames? I just wonder how it got kind of weird like this.

You might run DSS options 1 and 2 for comparison, and see if those also have strange color/background problems.

The whole thing might not look too bad in grayscale!

The comet processed reasonably well I think, structurally anyway. Mind the stretch in order to suppress a bunch of that diagonal noise. Unknown if true walking noise or a result of the comet stacking. Did you dither at all? Not that I know if it is useful here; I am not a comet expert!

Color was basically impossible, so I just made a star mask and ran the target, then inverted and ran the stars through color separately. The channel bias I just adjusted by eye, and may have zero basis in reality.

It really didn't work so great, but it was something. Then I used SS followed by a strong denoise with walking noise angle set to match that diagonal. After tracking I used FilmDev to drop the gamma a bit further.

I wonder if 60 seconds might be a bit long, especially at this scale, both for comet motion and star saturation?

moonstruck Comet-Autosave ST9 1B.jpg (402.79 KiB) Viewed 17085 times

EDIT: Did you see that tiny little galaxy you captured below the comet? If you look that up using your location and the acquisition date/time you might be able to ID it.

[Moonstruck]

Thanks Mike. I also took 30-sec subs a few days ago, but with those the tail was way too faint so I increased the exposure time. I have been at this for a few days now... I now have 30, 45, 60, 120 and 180 sec subs to experiment with. Your processing info is very helpful, and I will try processing it again. If I can figure out how to run dss with the other two options I'll also give that a try. On the positive side I didn't have any star trailing issues... if I can get rid of the weird background coloring/noise I can live with the rest of it. In the version you saw I used calibration frames taken from an earlier session the day before (flats, darks, dark flats); not sure I was supposed to do that. I also tried processing it with no calibration frames to see if they had a negative effect, but the strange background was still there so I don't think they adversely affected the picture.

I have seen a lot of great pictures of this comet on line and the sub times ranged from 10 secs to over 5 min., so I am not really sure how that (or total exposure time) factors in. You'd think sub times over a minute or so would blow out the core, but I saw one shot with 180-sec subs that was truly amazing.

I didn't see the galaxy you mentioned but will have a closer look! In one of my earlier captures I saw a needle galaxy above the comet, which was cool. I didn't have time to go back and look it up though. You never know what additional surprises you will get!

Today I will try to process the 45, 120 and 180 sec subs. Fingers crossed. Thanks again.

John

[wonky5#]

I thought I would take a stab at it. I didn't artificially "color" anything. I made a star mask in the color module with some of the brightest stars, and used those for a sample, then masked everything and this is what I got. I processed it a few different ways, but it seemed the predominate color on the was purple. I know some of the stars are green and have "rings", but I was just trying to see if there was color there-there certainly is. Most all of the pictures show more green around the nucleous, but I have seen a few with purple in the tail. It needs more work on the stars, but I think it's a great photo, far better than what I'll probably get if the clouds ever break!

[Moonstruck]

Thanks wonky5- I appreciate you processing it. It really helps to see what others do with the same data. I also ended up with a purple or pink hue in several of my attempts. I am going to give this another shot with several different exposure times.

[happy-kat]

My DSS comet stack has very problematic background so have done a stack in siril and have been able to process that better.